When shocks rang out in the shadow of the nation's capitol, during a federal government shutdown, in an era of deranged spree killings, all sorts of nightmare scenarios leap into the imagination. But this time it was not a gunman opening fire, but capitol hill police after a woman with a baby in her car rammed white house barricade after a high-speed chase, the woman was shot dead. The child is safe. Who was this suspect? And was postpartum depression partly to blame for the episode? As the search for answers continues tonight here is abc's senior national correspondent jim avila. Reporter: It was 47 minutes of supreme chaos. That shut down washington, into capitol lockdown. A high speed car chase from one end of the famous stretch of pennsylvania avenue to the other. White house to capitol hill. Leaving two officers wounded, the driver dead, and a startling dis discovery, a baby in the back seat. The driver of the black infinity sedan ran into a barrier on the southeast side of the white house. The barrier fell down. And at that point secret service was getting reactive. Trying to stop them. And then just took off. Reporter: Police immediately swarmed the scene. But the driver pulled away, careening down the street. By 2:30, she stopped at the botanical gardens. Look again as she is surrounded by police, guns drawn. A patrol car tried to block her. She reversed and was off again as police fired on the fleeing vehicle. It was a two-door, dark coup. It looked like to me. Shortly after they arrived i heard the gunshots and then the car tore out of the area back to this direct, with the police cars following. The entire government corridor from the president's house to the nation's capital was placed on lockdown. The black car circled the peace memorial at a dangerous speed as captured by a cameraman, for an arab language broadcaster funded by the u.S. Government to gather news for middle east viewers overseas. Reporter: The driver raced up constitution avenue past the skcop t -- capitol. Stopped by the supreme court. Gunshots rang out and heard across the capital. Baron soko was in his company office overlooking the scene. I was on a call with the windows open. I heard gunfire. Dr dropped to the floor. It was rapid. Eight to ten shots. And once that was over, I got up and -- looked out the window on to constitution avenue. Reporter: The smell of gunfire in the air, baron began shooting pictures and tweeting what he saw. There were probably 30 cops, many in body armor with machine guns, armored personnel carrier came in five minutes later. Reporter: Heavy duty stuff was there? Very heavy. They were clearing the scene. What added to the, the feel of it was the, the smell of gunpowder. Call Reporter: Skocongressmen were told to hide their identities. A police officer came running. Are you a member of congress? I am. Let me see your identification. I pulled out my identification. Take your pin off. We wear these little pins around. So he told me to take the pin off. You could be a target. Reporter: On the floor of the senate, all proceedings are ordered to stop. We thought we heard shots. Saw a lot of police cars. Then we heard shots. Then the police told to us go back. We were walking back to the office. We heard shots. Sounded like shots. Let's go! Reporter: The suspect was shot and taken to a nearby hospital where she died. A capitol police officer injured when his car hit a capitol barricade was also hospitalized. As was a secret service agent, bumped by the car at the white house. Inside the suspect's car, there were no weapons. Something more alarming. A 1-year-old baby unhurt. The child is approximately a year old in good condition in protective custody. It does not appear any way this is an accident. Reporter: Tonight police are investigating the home of miriam carey whose family members tell abc news she is the woman police believe was involved in the accident a cording to a family. A 34-year-old dental hygienist suffering from postpartum depression. Today's chaos could not have come at a more tense time for washington. This company town all ready on edge because of a government shutdown. And still recovering from the terrible violence of just a few weeks ago, a few miles away, from today's incident. When a lone gunman, 34-year-old aaron alexis stormed washington's navy yard with a shotgun and handgun. On the fourth floor. Shotgun multiple shots fired. Multiple people down. We are still waiting. Alexis, a government technology contractor used security clearances to march through the building where 3,000 military and civilian personnel work. The fbi released these surveillance tapes of alexis haunting the hauls, hunting for innocent targets. 1:30 into the rampage. Alexis was shot to death exchanging gunfire with police more than an hour. 12 innocent people were killed. Four wounded. It appears aaron alexis had a history of mental illness, hearing voices in his head and being taunted by microwaves. There are multiple indicators that alexis held a delusional belief he was being controlled or influenced by extremely low frequency or elf, electromagnetic waves. The horrifying navy yard attack stunned the capital. Later that same evening, a burst of pops were heard in front of the white house sending night lockdown. Secret service agents tackled a man. It turns out the pops were nothing more than firecrackers. If you live in washington, there is always a certain risk of something happening. You are not surprised if something happens. Today's wild chase comes during a bitter partisa standoff. The shutdown that for the capitol police officers involved meant all work and no pay. All were required to work at their jobs, but they will get no checks until after the stalemate is over. As the the lockdown ended, congress took a moment to acknowledge the chaos outside. Madam speaker with your permission I ask for a moment of silent prayer for those officers injured today. Reporter: A brief moment of agreement in what this week has been anything but an agreeable town. For "nightline," jim avila, at the capitol.

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